Metal additive manufacturing using gas mixture including oxygen

ABSTRACT

A metal powder additive manufacturing system and method are disclosed that use increased trace amounts of oxygen to improve physical attributes of an object. The system may include: a processing chamber; a metal powder bed within the processing chamber; a melting element configured to sequentially melt layers of metal powder on the metal powder bed to generate an object; and a control system configured to control a flow of a gas mixture within the processing chamber from a source of inert gas and a source of an oxygen containing material, the gas mixture including the inert gas and oxygen from the oxygen containing material. The method may result in an object having a surface porosity of no greater than approximately 0.1%, and an effective density of greater than approximately 99.9%.

This application is a continuation-in-part application of U.S.application Ser. No. 14/981321, filed Dec. 28, 2015, currently pending.

BACKGROUND OF THE INVENTION

The disclosure relates generally to additive manufacturing, and moreparticularly, to a metal additive manufacturing system that employs agas mixture including oxygen. The disclosure also relates to metaladditive manufacturing methods and an object formed using the methods.

Additive manufacturing (AM) includes a wide variety of processes ofproducing an object through the successive layering of material ratherthan the removal of material. As such, additive manufacturing can createcomplex geometries without the use of any sort of tools, molds orfixtures, and with little or no waste material. Instead of machiningcomponents from solid billets of material, much of which is cut away anddiscarded, the only material used in additive manufacturing is what isrequired to shape the object.

Additive manufacturing techniques typically include taking athree-dimensional computer aided design (CAD) file of the object to beformed, electronically slicing the object into layers, e.g., 18-102micrometers thick, and creating a file with a two-dimensional image ofeach layer. The file may then be loaded into a preparation softwaresystem that interprets the file such that the object can be built bydifferent types of additive manufacturing systems. In 3D printing, rapidprototyping (RP), and direct digital manufacturing (DDM) forms ofadditive manufacturing, material layers are selectively dispensed tocreate the object.

In metal powder additive manufacturing techniques, such as selectivelaser melting (SLM) and direct metal laser melting (DMLM), metal powderlayers are sequentially melted together to form the object. Morespecifically, fine metal powder layers are sequentially melted afterbeing uniformly distributed using an applicator on a metal powder bed.The metal powder bed can be moved in a vertical axis. The process takesplace in a processing chamber having a precisely controlled atmosphereof inert gas, e.g., argon or nitrogen, at strictly enforced oxygenlevels below 500 parts per million or less than 0.1% of the volume inthe processing chamber. Once each layer is created, each two dimensionalslice of the object geometry can be fused by selectively melting themetal powder. The melting may be performed by a high powered laser, suchas a 100 Watt ytterbium laser. The laser moves in the X-Y directionusing scanning mirrors, and has an intensity sufficient to fully weld(melt) the metal powder to form a solid metal. The metal powder bed islowered for each subsequent two dimensional layer, and the processrepeats until the object is completely formed. Obtaining the appropriategas mixture environment in metal powder additive manufacturing hasproven a challenge. Consequently, achieving desired surface finishes,part efficiency and part density can be difficult using metal powderadditive manufacturing.

BRIEF DESCRIPTION OF THE INVENTION

A first aspect of the disclosure provides a metal powder additivemanufacturing system, the system comprising: a processing chamber; ametal powder bed within the processing chamber; a melting elementconfigured to sequentially melt layers of metal powder on the metalpowder bed to generate an object; and a control system configured tocontrol a flow of a gas mixture within the processing chamber from asource of inert gas and a source of an oxygen containing material, thegas mixture including the inert gas and oxygen from the oxygencontaining material.

A second aspect of the disclosure provides a metal powder additivemanufacturing method, the method comprising: providing a metal powderbed within a processing chamber; controlling a flow of a gas mixturewithin the processing chamber from a source of inert gas and a source ofan oxygen containing material, the gas mixture including the inert gasand oxygen from the oxygen containing material; and sequentially meltinglayers of metal powder on the metal powder bed to generate an object.

A third aspect of the disclosure relates to an object formed by a metalpowder additive manufacturing method, the method comprising: providing ametal powder bed within a processing chamber; controlling a flow of agas mixture within the processing chamber from a source of inert gas anda source of an oxygen containing material, the gas mixture including theinert gas and oxygen from the oxygen containing material; andsequentially melting layers of metal powder on the metal powder bed togenerate the object, wherein the object has a surface porosity of nogreater than approximately 0.1%.

The illustrative aspects of the present disclosure are designed to solvethe problems herein described and/or other problems not discussed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this disclosure will be more readilyunderstood from the following detailed description of the variousaspects of the disclosure taken in conjunction with the accompanyingdrawings that depict various embodiments of the disclosure, in which:

FIG. 1 shows a block diagram of a metal powder additive manufacturingsystem according to embodiments of the disclosure.

It is noted that the drawings of the disclosure are not to scale. Thedrawings are intended to depict only typical aspects of the disclosure,and therefore should not be considered as limiting the scope of thedisclosure. In the drawings, like numbering represents like elementsbetween the drawings.

DETAILED DESCRIPTION OF THE INVENTION

As indicated above, the disclosure provides a metal powder additivemanufacturing system and method that uses a gas mixture including oxygenat higher levels than conventionally employed to better control, forexample, object surface porosity and effective density. It has also beendiscovered that the teachings of the disclosure provide dramaticincreases in effective filter life on metal powder additivemanufacturing systems.

Referring to the drawings, FIG. 1 shows a schematic/block view of anillustrative metal powder additive manufacturing system 100 forgenerating an object 102, of which only an upper surface is shown. Inthis example, system 100 is arranged for direct metal laser melting(DMLM). It is understood that the general teachings of the disclosureare equally applicable to other forms of metal powder additivemanufacturing such as selective laser melting (SLM). Object 102 isillustrated as a double walled turbine element; however, it isunderstood that the additive manufacturing process can be readilyadapted to manufacture many other parts.

System 100 generally includes a metal powder additive manufacturingcontrol system 104 (“control system”) and an AM printer 106. As will bedescribed, control system 104 executes code 108 to generate object 102.Control system 104 is shown implemented on computer 110 as computerprogram code. To this extent, computer 110 is shown including a memory112, a processor 114, an input/output (I/O) interface 116, and a bus118. Further, computer 110 is shown in communication with an externalI/O device/resource 120 and a storage system 122. In general, processor114 executes computer program code 108 that is stored in memory 112and/or storage system 112. While executing computer program code 108,processor 114 can read and/or write data to/from memory 112, storagesystem 122, I/O device 120 and/or AM printer 106. Bus 118 provides acommunication link between each of the components in computer 110, andI/O device 120 can comprise any device that enables a user to interactwith computer 110 (e.g., keyboard, pointing device, display, etc.).Computer 110 is only representative of various possible combinations ofhardware and software. For example, processor 114 may comprise a singleprocessing unit, or be distributed across one or more processing unitsin one or more locations, e.g., on a client and server. Similarly,memory 112 and/or storage system 122 may reside at one or more physicallocations. Memory 112 and/or storage system 122 can comprise anycombination of various types of non-transitory computer readable storagemedium including magnetic media, optical media, random access memory(RAM), read only memory (ROM), etc. Computer 110 can comprise any typeof computing device such as an industrial controller, a network server,a desktop computer, a laptop, a handheld device, etc.

As noted, system 100 and in particular control system 104 executes code108 to generate object 102. Code 108 can include, inter alia, a set ofcomputer-executable instructions 108S for operating AM printer 106 and aset of computer-executable instructions 108O defining object 102 to bephysically generated by AM printer 106. As described herein, additivemanufacturing processes begin with a non-transitory computer readablestorage medium (e.g., memory 112, storage system 122, etc.) storing code108. Set of computer-executable instructions 108S for operating AMprinter 106 may include any now known or later developed software codecapable of operating AM printer 106. Set of computer-executableinstructions 108O defining object 102 may include a precisely defined 3Dmodel of an object and can be generated from any of a large variety ofwell-known computer aided design (CAD) software systems such asAutoCAD®, TurboCAD®, DesignCAD 3D Max, etc. In this regard, code 108Ocan include any now known or later developed file format. Furthermore,code 108O representative of object 102 may be translated betweendifferent formats. For example, code 108O may include StandardTessellation Language (STL) files which was created forstereolithography CAD programs of 3D Systems, or an additivemanufacturing file (AMF), which is an American Society of MechanicalEngineers (ASME) standard that is an extensible markup-language (XML)based format designed to allow any CAD software to describe the shapeand composition of any three-dimensional object to be fabricated on anyAM printer. Code 108O representative of object 102 may also be convertedinto a set of data signals and transmitted, received as a set of datasignals and converted to code, stored, etc., as necessary. In any event,code 108O may be an input to system 100 and may come from a partdesigner, an intellectual property (IP) provider, a design company, theoperator or owner of system 100, or from other sources. In any event,control system 104 executes code 108S and 108O, dividing object 102 intoa series of thin slices that it assembles using AM printer 106 insuccessive layers of material.

AM printer 106 may include a processing chamber 130 that is sealed toprovide a controlled atmosphere for object 102 printing. A metal powderbed or platform 132, upon which object 102 is built, is positionedwithin processing chamber 130. A melting element 134 is configured tosequentially melt layers of metal powder on metal powder bed 132 togenerate object 102. In this regard, melting element 134 may generateone or more laser or electron beams 138 that fuse particles for eachslice, as defined by code 108. An applicator 140 may create a thin layerof raw material 142 spread out as the blank canvas from which eachsuccessive slice of the final object will be created. Various parts ofAM printer 106 may move to accommodate the addition of each new layer,e.g., a metal powder bed 132 may lower and/or chamber 130 and/orapplicator 140 may rise after each layer. The process may use differentraw materials in the form of fine-grain metal powder, a stock of whichmay be held in a chamber 144 accessible by applicator 140. In theinstant case, object 102 may be made of a “metal” which may include apure metal or an alloy. In one example, the metal may includepractically any non-reactive metal powder, i.e., non-explosive ornon-conductive powder, such as but not limited to: a cobalt chromiummolybdenum (CoCrMo) alloy, stainless steel, an austenite nickel-chromiumbased alloy such as a nickel-chromium-molybdenum-niobium alloy(NiCrMoNb) (e.g., Inconel 625 or Inconel 718), anickel-chromium-iron-molybdenum alloy (NiCrFeMo) (e.g., Hastelloy® Xavailable from Haynes International, Inc.), or anickel-chromium-cobalt-molybdenum alloy (NiCrCoMo) (e.g., Haynes 282available from Haynes International, Inc.), etc.

With further regard to processing chamber 130 and the atmospheretherein, as noted herein, in conventional systems, the chamber is filledwith an inert gas such as argon or nitrogen and controlled to minimizeor eliminate oxygen. In accordance with embodiments of the disclosure,increased trace amounts of oxygen have been found to advantageouslychange the melt pool characteristics of object 102 resulting in a higherdensity part and substantial improvements in the overall surface finishof the as-built part. In contrast to conventional systems, embodimentsof the disclosure have control system 104 configured to control a flowof a gas mixture 160 within processing chamber 130 from a source ofinert gas 154 and a source of an oxygen containing material 162. In thiscase, control system 104 may control a pump 150, and/or a flow valvesystem 152 for inert gas and a flow valve system 164 for oxygencontaining material, to control the content of gas mixture 160. That is,control system 104 controls at least one of: flow valve system 152coupled to source of inert gas 154, flow valve system 164 coupled tosource of oxygen containing material 162, and pump 150 coupled to sourceof inert gas 154 and source of oxygen containing material 162. Each flowvalve system 152, 164 may include one or more computer controllablevalves, flow sensors, temperature sensors, pressure sensors, etc.,capable of precisely controlling flow of the particular gas or material.Pump 150 may be provided with our without valve systems 152, 164. Wherepump 150 is omitted, inert gas and oxygen containing material may simplymix together in a conduit or manifold prior to introduction toprocessing chamber 130. Source of inert gas 154 or source of oxygencontaining material 162 may take the form of any conventional source forthe material contained therein, e.g. a tank, reservoir or other source.Any sensors (not shown) required to measure the particular materials maybe provided. In any event, gas mixture 160 includes inert gas and oxygenfrom the oxygen containing material. In one embodiment, a volumepercentage of oxygen in gas mixture 160 may be between approximately0.25% to approximately 1%, i.e., significantly higher than inconventional systems. As used herein, “approximately” indicates +/−10%of the value or, if a range, values stated. Gas mixture 160 may befiltered using a filter 170 in a conventional manner.

The inert gas can include any of the aforementioned gases, e.g., argonor nitrogen, perhaps with some helium. The oxygen contain material cantake a variety of forms. In one embodiment, the oxygen containingmaterial may include an oxygen containing gas, such as air or pureoxygen (the latter having >99% O₂), each of which can be provided in acompressed form in a conventional fashion. Where the oxygen containingmaterial includes inert gases, such as the case with air carrying inertgases such as nitrogen, the amounts of inert gas (and/or oxygencontaining material) may be altered to accommodate the increased volumesof inert gas. In another embodiment, the oxygen containing material mayinclude water, which may be applied, for example, by introducing waterto paper gas filters in a filtering system, allowing the gas mixture toabsorb moisture as it passes through the paper filters. In this latterexample, provisions (not shown) may be necessary to remove condensatewithin processing chamber 130. According to embodiments of thedisclosure, introduction of water provides additional oxygen to gasmixture 160, as described herein, and also improves filter 170operation. Accordingly, as an optional embodiment, filter 170 may bemoistened with water, e.g., by spraying water or dipping filter 170 intowater prior to operation, to improve its filtering effectiveness and tointroduce some oxygen to gas mixture 160. It is also envisioned that avariety of other oxygen containing materials could be employed withinthe scope of the disclosure, perhaps with other structure to separatethe oxygen out of any carrier such as, but not limited to: carbondioxide (CO₂), iron oxide (FeO), silicon dioxide (SiO₂), chromium oxide(Cr₂O₃) and manganese monoxide (MnO).

In operation, metal powder bed 132 is provided within processing chamber130, and control system 104 controls flow of gas mixture 160 withinprocessing chamber 130 from source of inert gas 154 and source of anoxygen containing material 162 such that gas mixture includes the inertgas and oxygen from the oxygen containing material. Control system 104also controls AM printer 106, and in particular, applicator 140 andmelting element 134, to sequentially melt layers of metal powder onmetal powder bed 132 to generate object 102. Object 102 createdaccording to embodiments of the disclosure exhibit a surface porosity ofno greater than approximately 0.1%, which is an improvement overconventional processes that do not employ as much oxygen. “Surfaceporosity” as used herein indicates accessible void space over totalexternal space of an object. Further, object 102 may have an effectivedensity of greater than approximately 99.9%, which is also animprovement over conventional processes that do not employ as muchoxygen. As used herein, “effective density” indicates an average density(e.g., in kilograms per cubic meter) of the object formed versus thedensity of the material of which it is made (in same units).

In most cases, control system 104 acts to maintain oxygen content in gasmixture 160 in the afore-mentioned range. Alternatively, control system104 may also change a percentage of oxygen in gas mixture 160 duringoperation of AM printer 106, e.g., metal powder bed 132 and meltingelement 134. In this fashion, object 102 manufacture could be ensured tohave consistent physical attributes, e.g., surface porosity, effectivedensity, etc., where other system parameters change, or object 102 canhave its physical properties altered in portions thereof, as dictated bycode 108O. In any event, once complete, object 102 may be exposed to anyvariety of finishing processes, e.g., minor machining, sealing,polishing, etc.

In one embodiment, system 100 can be created by modifying a number ofconventional metal powder additive manufacturing systems such as a model280HL selective laser melting system available from SLM Solutions GroupAG, Lubeck Germany, or similar models available from EOS GmbH ElectroOptical Systems, Munich Germany; Concept Laser GmbH, LichtenfelsGermany; and 3D Systems, Rock Hill Inc., South Carolina, USA.

System 100 provides a better as-built surface finish for object 102,e.g., surface porosity, and denser as-built objects 102. Consequently,system 100 provides a wider process window for acceptable part quality.In addition, system 100 has been found to increase the life of gasmixture filter 170, resulting in decreased consumable operating costs.

As will be appreciated by one skilled in the art, parts of system 100 ofthe present disclosure may be embodied as a system, method or computerprogram product. Accordingly, control system 104 may take the form of anentirely hardware embodiment, an entirely software embodiment (includingfirmware, resident software, micro-code, etc.) or an embodimentcombining software and hardware aspects that may all generally bereferred to herein as a “circuit,” “module” or “system.” Furthermore,the present disclosure may take the form of a computer program productembodied in any tangible medium of expression having computer-usableprogram code embodied in the medium.

Any combination of one or more computer usable or computer readablemedium(s) may be utilized. The computer-usable or computer-readablemedium may be, for example but not limited to, an electronic, magnetic,optical, electromagnetic, infrared, or semiconductor system, apparatus,device, or propagation medium. More specific examples (a non-exhaustivelist) of the computer-readable medium would include the following: anelectrical connection having one or more wires, a portable computerdiskette, a hard disk, a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flashmemory), an optical fiber, a portable compact disc read-only memory(CD-ROM), an optical storage device, a transmission media such as thosesupporting the Internet or an intranet, or a magnetic storage device.Note that the computer-usable or computer-readable medium could even bepaper or another suitable medium upon which the program is printed, asthe program can be electronically captured, via, for instance, opticalscanning of the paper or other medium, then compiled, interpreted, orotherwise processed in a suitable manner, if necessary, and then storedin a computer memory. In the context of this document, a computer-usableor computer-readable medium may be any medium that can contain, store,communicate, propagate, or transport the program for use by or inconnection with the instruction execution system, apparatus, or device.The computer-usable medium may include a propagated data signal with thecomputer-usable program code embodied therewith, either in baseband oras part of a carrier wave. The computer usable program code may betransmitted using any appropriate medium, including but not limited towireless, wireline, optical fiber cable, RF, etc.

Computer program code for carrying out operations of the presentdisclosure may be written in any combination of one or more programminglanguages, including an object oriented programming language such asJava, Smalltalk, C++ or the like and conventional procedural programminglanguages, such as the “C” programming language or similar programminglanguages. The program code may execute entirely on the user's computer,partly on the user's computer, as a stand-alone software package, partlyon the user's computer and partly on a remote computer or entirely onthe remote computer or server. In the latter scenario, the remotecomputer may be connected to the user's computer through any type ofnetwork, including a local area network (LAN) or a wide area network(WAN), or the connection may be made to an external computer (forexample, through the Internet using an Internet Service Provider).

These computer program instructions may also be stored in acomputer-readable medium that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablemedium produce an article of manufacture including instruction meanswhich implement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer orother programmable data processing apparatus to cause a series ofoperational steps to be performed on the computer or other programmableapparatus to produce a computer implemented process such that theinstructions which execute on the computer or other programmableapparatus provide processes for implementing the functions/actsspecified in the flowchart and/or block diagram block or blocks.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present disclosure has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the disclosure in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the disclosure. Theembodiment was chosen and described in order to best explain theprinciples of the disclosure and the practical application, and toenable others of ordinary skill in the art to understand the disclosurefor various embodiments with various modifications as are suited to theparticular use contemplated.

What is claimed is:
 1. A metal powder additive manufacturing system, thesystem comprising: a processing chamber; a metal powder bed within theprocessing chamber; a melting element configured to sequentially meltlayers of metal powder on the metal powder bed to generate an object;and a control system configured to control a flow of a gas mixturewithin the processing chamber from a source of inert gas and a source ofan oxygen containing material, the gas mixture including the inert gasand oxygen from the oxygen containing material.
 2. The system of claim1, wherein the oxygen containing material includes an oxygen containinggas.
 3. The system of claim 2, wherein the oxygen containing gasincludes air.
 4. The system of claim 2, wherein the oxygen containinggas includes pure oxygen.
 5. The system of claim 1, wherein the oxygencontaining material includes water.
 6. The system of claim 1, wherein avolume percentage of oxygen in the gas mixture is between approximately0.25% to approximately 1%. The system of claim 1, wherein the metalpowder includes a non-reactive metal powder.
 8. The system of claim 1,wherein the metal powder is selected from the group consisting of: acobalt chromium molybdenum (CoCrMo) alloy, stainless steel, anickel-chromium-molybdenum-niobium (NiCrMoNb) alloy, anickel-chromium-iron-molybdenum (NiCrFeMo) alloy, and anickel-chromium-cobalt-molybdenum (NiCrCoMo) alloy.
 9. The system ofclaim 1, wherein the object has a surface porosity of no greater thanapproximately 0.1%.
 10. The system of claim 1, wherein the object has aneffective density of greater than approximately 99.9%.
 11. The system ofclaim 1, wherein the inert gas is chosen from the group consisting of:argon and nitrogen.
 12. The system of claim 1, wherein the controlsystem controls at least one of: a flow valve system coupled to thesource of inert gas, a flow valve system coupled to the source of oxygencontaining material and a pump coupled to the source of inert gas andthe source of oxygen containing material.
 13. The system of claim 1,wherein the control system changes a percentage of oxygen in the gasmixture during operation of the metal powder bed and the laser meltingelement.
 14. A metal powder additive manufacturing method, the methodcomprising: providing a metal powder bed within a processing chamber;controlling a flow of a gas mixture within the processing chamber from asource of inert gas and a source of an oxygen containing material, thegas mixture including the inert gas and oxygen from the oxygencontaining material; and sequentially melting layers of metal powder onthe metal powder bed to generate an object.
 15. The method of claim 14,wherein the oxygen containing material includes an oxygen containinggas.
 16. The method of claim 15, wherein the oxygen containing gasincludes air.
 17. The method of claim 15, wherein the oxygen containinggas includes pure oxygen.
 18. The method of claim 14, wherein the oxygencontaining material includes water.
 19. The method of claim 14, whereina volume percentage of oxygen in the gas mixture is betweenapproximately 0.25% to approximately 1%.
 20. The method of claim 14,wherein the metal powder includes a non-reactive metal powder.
 21. Themethod of claim 14, wherein the metal powder is selected from the groupconsisting of: a cobalt chromium molybdenum (CoCrMo) alloy, stainlesssteel, a nickel-chromium-molybdenum-niobium (NiCrMoNb) alloy, anickel-chromium-iron-molybdenum (NiCrFeMo) alloy, and anickel-chromium-cobalt-molybdenum (NiCrCoMo) alloy.
 22. The method ofclaim 14, wherein the object has a surface porosity of no greater thanapproximately 0.1%.
 23. The method of claim 14, wherein the object hasan effective density of greater than approximately 99.9%.
 24. The methodof claim 14, wherein the inert gas is chosen from the group consistingof: argon and nitrogen.
 25. An object formed by a metal powder additivemanufacturing method, the method comprising: providing a metal powderbed within a processing chamber; controlling a flow of a gas mixturewithin the processing chamber from a source of inert gas and a source ofan oxygen containing material, the gas mixture including the inert gasand oxygen from the oxygen containing material; and sequentially meltinglayers of metal powder on the metal powder bed to generate the object,wherein the object has a surface porosity of no greater thanapproximately 0.1%.
 26. The method of claim 25, wherein the oxygencontaining material includes an oxygen containing gas.
 27. The method ofclaim 25, wherein the oxygen containing material includes water.
 28. Themethod of claim 25, wherein a volume percentage of oxygen in the gasmixture is between approximately 0.25% to approximately 1%.
 29. Themethod of claim 25, wherein the metal powder is selected from the groupconsisting of: a cobalt chromium molybdenum (CoCrMo) alloy, stainlesssteel, a nickel-chromium-molybdenum-niobium (NiCrMoNb) alloy, anickel-chromium-iron-molybdenum (NiCrFeMo) alloy, and anickel-chromium-cobalt-molybdenum (NiCrCoMo) alloy.
 30. The method ofclaim 25, wherein the object has an effective density of greater thanapproximately 99.9%.